BERLIN - German union Verdi called a public transport strike across Europe’s biggest economy on Friday, in an escalating dispute over pay and working conditions. More than 90,000 workers at over 132 local companies operating buses, trams and underground services are expected to join the walkout. Long-distance and regional trains operated by Deutsche Bahn, which went on strike last week, will not be affected. Friday’s walkout is the latest in a spate of strikes and protests to hit commuters in the last weeks. Verdi’s deputy chair Christine Behle said the union was seeking a 35-hour work week with no losses in wages, in a bid to make jobs more attractive to workers. Many operators are reporting up to 20 to 30 percent unfilled posts, with the worker shortages contributing to a vicious cycle of overworked employees who are then falling ill, exacerbating the situation.